The present invention relates to a space light modulating apparatus and a stereoscopic display apparatus which are used for a rewritable hologram stereoscopic display and, more particularly, to a space light modulating apparatus and a stereoscopic display apparatus which can display a solid image at a practical pixel density.
A stereoscopic display is a method of enabling a structure such as depth, thickness, or the like of a 3-dimensional object to be easily visually understood. Such a stereoscopic display is largely demanded in the display field of the structure designed by a CAD or the like or the display field of a medical image. The stereoscopic display has a feeling of a reality, is impressive as compared with the 2-dimensional display, and is also used in the display for amusement in an amusement park, a movie, or the like.
A conventional rewritable hologram stereoscopic display apparatus is realized by using, for example, an acoustic optical element (AOM) for generating a calculated 1-dimensional interference fringe, a rotary mirror, a galvano mirror, a reducing lens, and the like (refer to "Practical Holography VI, #1212-20", SPIE Proc., Vol. 1212, 1990). Since such an apparatus has mechanical movable portions, however, there is a drawback such that it is difficult to realize a large screen and to miniaturize the apparatus.
On the other hand, in association with the recent improvement of the performance of the liquid crystal display apparatus, a space light modulating apparatus which can dynamically change a hologram has been examined. There has been proposed an apparatus in which a phase distribution of the hologram is displayed by using a liquid crystal display apparatus and a solid image is reconstructed by irradiating an illuminate light to the phase distribution (refer to JP-A-64-84933). According to such an apparatus, since the hologram is rewritten by an electrical control, the apparatus can be miniaturized by the installing technique of driving electronic circuits.
In the display of the phase distribution of the hologram using such a conventional liquid crystal display apparatus, however, according to the present technique, a pixel density of the ordinary liquid crystal display apparatus is equal to a value on the order of about 10.sup.3 per line and is not so fine, so that it is difficult to express an interference fringe of a high spatial frequency, namely, a phase distribution. That is, in order to display a solid image in front of the space light modulating apparatus or in a wide visual field, a space light modulating element which can display an interference fringe at a high spatial frequency is needed. According to the pixel density of the present liquid crystal display apparatus, however, there is a problem such that an interference fringe at a high spatial frequency cannot be produced.